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The Eigenvector 1 schema, or the main sequence of quasars, was introduced as an analogous scheme to the HR diagram that would allow us to understand the more complex, extended sources -active galactic nuclei (AGNs) that harbor accreting supermassive black holes. The study has spanned more than three decades and has advanced our knowledge of the diversity of Type-1 AGNs from both observational and theoretical aspects. The quasar main sequence, in its simplest form, is the plane between the FWHM of the broad Hβ emission line and the strength of the optical Fe II emission to the Hβ. While the former allows the estimation of the black hole mass, the latter enables direct measurement of the metal content and traces the accretion rate of the AGN. Together, they allow us to track the evolution of AGN in terms of the activity of the central nuclei, its effect on the line-emitting regions surrounding the AGN, and their diversity making them suitable distance indicators to study the expansion of our Universe. This mini-reviewaims to provide (i) a brief history leading up to the present day in the study of the quasar main sequence, (ii) introduce us to the many possibilities to study AGNs with the main sequence as a guiding tool, and (iii) highlight some recent, exciting lines of researches at the frontier of this ever-growing field. [ABSTRACT FROM AUTHOR]

We present the first measurement of H i mass of star-forming galaxies in different large scale structure environments from a blind survey at z ∼ 0.37. In particular, we carry out a spectral line stacking analysis considering 2875 spectra of colour-selected star-forming galaxies undetected in H i at 0.23 < z < 0.49 in the COSMOS field, extracted from the MIGHTEE-H i Early Science data cubes, acquired with the MeerKAT radio telescope. We stack galaxies belonging to different subsamples depending on three different definitions of large-scale structure environment: local galaxy overdensity, position inside the host dark matter halo (central, satellite, or isolated), and cosmic web type (field, filament, or knot). We first stack the full star-forming galaxy sample and find a robust H i detection yielding an average galaxy H i mass of |$M_{\rm H \, {\small I}}=(8.12\pm 0.75)\times 10^9\, {\rm M}_\odot$| at ∼11.8σ. Next, we investigate the different subsamples finding a negligible difference in M H i as a function of the galaxy overdensity. We report an H i excess compared to the full sample in satellite galaxies (M H i  = (11.31 ± 1.22) × 109, at ∼10.2σ) and in filaments (M H i  = (11.62 ± 0.90) × 109. Conversely, we report non-detections for the central and knot galaxies subsamples, which appear to be H i -deficient. We find the same qualitative results also when stacking in units of H i fraction (f H i ). We conclude that the H i amount in star-forming galaxies at the studied redshifts correlates with the large-scale structure environment. [ABSTRACT FROM AUTHOR]

Constraining the physical conditions of the ionized media in the vicinity of an active supermassive black hole (SMBH) is crucial to understanding how these complex systems operate. Metal emission lines such as iron (Fe) are useful probes to trace the gaseous media's abundance, activity, and evolution in these accreting systems. Among these, the Feii emission has been the focus of many prior studies to investigate the energetics, kinematics, and composition of the broad-emission line region (BELR) from where these emission lines are produced. In this paper, we present the first simultaneous Feii modeling in the optical and near-infrared (NIR) regions. We use cloudy photoionization code to simulate both spectral regions in the wavelength interval 4000–12,000 Å. We compare our model predictions with the observed line flux ratios for I Zw (Zwicky) 1—a prototypical strong Feii-emitting active galactic nuclei (AGNs). This allows setting constraints on the BLR cloud density and metal content that is optimal for the production of the Feii emission, which can be extended to I Zw 1-like sources by examining a broad parameter space. We demonstrate the salient and distinct features of the Feii pseudo-continuum in the optical and NIR, giving special attention to the effect of micro-turbulence on the intensity of the Feii emission. [ABSTRACT FROM AUTHOR]

Properties of the broad line region (BLR) in active galactic nuclei (AGNs) are commonly used to estimate the mass of the supermassive black hole (SMBH) that powers an AGN. However, the understanding of the physics behind the BLR remains incomplete. The AGNs exhibit strong optical variability, observed in the change of the profiles and fluxes of broad emission lines. Utilizing this variability provides an opportunity to constrain the physics of the BLR, and understand the interplay of the BLR with SMBH and surrounding regions. Here, we present the long-term monitoring campaign of a sample of the known broad-line AGNs (identified as LoTerm AGN). The aim of this study is to show the importance of sustained and dedicated campaigns that continually collect spectroscopic data of the known AGNs over extended timescales, providing unique insight into the origin and structure of the BLR. LoTerm AGN is a collaborative network of seven moderate-size telescopes equipped for spectroscopy. We focus on the recent spectral data of the known changing-look AGN, NGC 3516. Specifically, we examine the broad hydrogen Balmer H α line observed in the period 2020–2023, demonstrating that this AGN remains active with the BLR signatures observed in the spectra. No significant change in the broad line profile of H α line is observed during this recent period. [ABSTRACT FROM AUTHOR]

We use archival WISE and Spitzer photometry to derive optical emission line fluxes for a sample of distant quasars at z∼6. We find evidence for exceptionally high equivalent width [OIII] emission (rest-frame EW∼400Å) similar to that inferred for star-forming galaxies at similar redshifts. The median H α and H β equivalent widths are derived to be ∼400Å and ∼100Å respectively, and are consistent with values seen among quasars in the local Universe, and at z ∼ 2. After accounting for the contribution of photoionization in the broad line regions of quasars, we suggest that the narrow [OIII] emission likely arises from feedback due to massive star-formation in the quasar host. Forthcoming mid-infrared spectroscopy with the James Webb Space Telescope will help constrain the physical conditions in quasar hosts further. [ABSTRACT FROM AUTHOR]

We present a review of the topics of X‐ray stellar tidal disruption events (TDEs) and changing‐look active galactic nuclei (AGN). Stars approaching a supermassive black hole (SMBH) can be tidally disrupted and accreted. TDEs were first discovered in the X‐ray regime and appear as luminous, giant‐amplitude flares from inactive galaxies. The early X‐ray observations with ROSAT also established the extreme X‐ray spectral softness of these events with temperatures of order 50–100 eV that continues to be seen in the majority of more recently identified events. While the majority of X‐ray TDEs has been identified from inactive galaxies and some showed the highest amplitudes of variability recorded from galaxy cores (amplitudes exceeding factors of 1000–6000), a small fraction of AGN has been found to be highly variable as well. In AGN, this so‐called changing‐look phenomenon often comes with a strong change in the optical broad emission lines, leading to Seyfert‐type changes between class 1 and class 2. These two forms of activity represent the extremes of variability among active and quiescent galaxies, and have opened up a new window to understanding accretion physics under extreme conditions. Finally, we introduce the term "frozen‐look AGN" to describe systems that show constant line emission despite dramatic changes in the observed ionizing continuum. These systems are best explained by strong changes of absorption along our line‐of‐sight. [ABSTRACT FROM AUTHOR]

Results of spectral studies of fifteen Seyfert galaxies at red wavelengths based on long-term observations are presented. In this range there are lines of hydrogen Hα, [NII], [OI], and [SII]. Data on the absolute emission fluxes in the emission lines and in the continuum at the wavelength of λ = 6400 Å are presented. In order to objectively compare the examined galaxies with one another, the values of their luminosities were calculated in absolute units with the distances to these objects taken into account. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study shows that the statistical equilibrium of Si II in the atmosphere of a B3 IV type star Her is extremely sensitive to a variation in photoionization cross-sections for the Si II levels. The difference in abundances derived from absorption lines of Si II between applying the data from two equal accuracy sources, namely, the Opacity Project (OP) and the NORAD database, amounts to 0.18 dex, on average. Using the hydrogenic approximation for photoionization cross-sections, we obtain the departure coefficients for the Si II S level, the source function for Si II 6371 Å, and the abundance derived from this line, which are very similar to the corresponding values computed by Takeda (2021). We suppose that close-to-solar abundance obtained by Takeda (2022) from Si II 6371 Å in Her is due to using the hydrogenic photoionization cross-sections for the Si II levels. However, emission lines of Si II observed in Her can only be reproduced with the OP photoionization cross-sections. Photoionization cross-sections for the Si II levels need further improvements. [ABSTRACT FROM AUTHOR]

One of the unique features of Visible Emission Line Coronagraph (VELC) on board Aditya-L1 mission is spectropolarimetric observations in coronal emission line centred at 10747 Å. Spectropolarimetric observations at 10747 Å helps in understanding coronal magnetic field topology and Line of Sight (LOS) field strength measurements. Coronal magnetic field measurements provide useful information about the drivers for space weather. To carry out the polarimetric observations a dual beam spectropolarimeter is employed in the VELC. Spectropolarimeter package consists of a Quarter Wave Plate (QWP), Polarizing Beam Displacer (PBD) and Half Wave Plate (HWP). Current manuscript provides an overview of the design of spectropolarimetric channel of VELC and the realization aspects. [ABSTRACT FROM AUTHOR]

We discuss the polarization of broad emission lines in the type 1 active galactic nuclei (AGN). The polarization depends on the geometry of the broad line region (BLR), and also on the polarization mechanism, or distribution of the scattering material. Therefore, the polarization measurements can indicate the geometry of the BLR and the mechanism of polarization (equatorial or polar scattering). In addition, the polarization angle (PA) shape across the line profile can be used to measure the supermassive black hole (SMBH) mass, and constrain the BLR characteristics. We give an overview of ours and other recent investigations of the polarization in broad lines from both aspects: theoretical and observational. [ABSTRACT FROM AUTHOR]

Several powerful outbursts have been observed during many years of observations of the symbiotic object MWC 560. The last active stage began in the autumn of 2018 and continues to the present. Observations of this event began at the Fesenkov Astrophysical Institute at the beginning of 2019. In our previous article we published the results obtained in early 2019. A light curve of the object and emission line profiles are presented; it is noted that a broad absorption band formed in a high velocity collimated jet vanishes. In this article we present the results of further spectral and photometric observations of MWC 560. It is to be noted that in 2021 the brightness of this object is sustained at a high level exceeding that obtained during the previous outbursts. In addition, at the end of 2020 a tendency toward a gradual weakening of the radiative fluxes in the emission lines was remarked. The profiles of all the lines have absorption components shifted to the "blue" by 52±5 km/s. It may be assumed that during this outburst there was partial (or complete) destruction of the accretion disk, so that the source of the high velocity collimated jet vanished. The gradual reduction in the radiative fluxes in the emission lines may be caused by a drop in the power of ionizing radiation. [ABSTRACT FROM AUTHOR]

This is a theoretical study of changes in several characteristics of the spectra of early-type supergiants owing to scattering of continuum radiation. Thomson scattering on free electrons is treated as the scattering mechanism, although the approach used here is quite general. The reason for changes in the spectral class of a star with constant bolometric luminosity and surface temperature is elucidated and the necessary conditions for their realization are introduced. The effect of scattering in the continuum on the magnitude of the intensity jumps in the hydrogen spectrum depending on the degree of ionization is studied. The conditions under which the Schuster mechanism for formation of emission lines sets in are clarified both for an isothermal atmosphere and for an atmosphere with a temperature gradient. [ABSTRACT FROM AUTHOR]

We carried out photometric and spectroscopic observations of the well-studied broad-line radio galaxy 3C 120 with the Las Cumbres Observatory (LCO) global robotic telescope network from 2016 December to 2018 April as part of the LCO AGN Key Project on Reverberation Mapping of Accretion Flows. Here, we present both spectroscopic and photometric reverberation mapping results. We used the interpolated cross-correlation function to perform multiple-line lag measurements in 3C 120. We find the H γ, He  ii λ4686, H β, and He  i λ5876 lags of |$\tau _{\text{cen}} = 18.8_{-1.0}^{+1.3}$|⁠ , |$2.7_{-0.8}^{+0.7}$|⁠ , |$21.2_{-1.0}^{+1.6}$|⁠ , and |$16.9_{-1.1}^{+0.9}$| d, respectively, relative to the V -band continuum. Using the measured lag and rms velocity width of the H β emission line, we determine the mass of the black hole for 3C 120 to be |$M=(6.3^{+0.5}_{-0.3})\times 10^7\, (f/5.5)$|  M⊙. Our black hole mass measurement is consistent with similar previous studies on 3C 120, but with small uncertainties. In addition, velocity-resolved lags in 3C 120 show a symmetric pattern across the H β line, 25 d at line centre decreasing to 17 d in the line wings at ±4000 km s−1. We also investigate the inter-band continuum lags in 3C 120 and find that they are generally consistent with τ ∝ λ4/3 as predicted from a geometrically thin, optically thick accretion disc. From the continuum lags, we measure the best-fitting value τ0 = 3.5 ± 0.2 d at |$\lambda _{\rm 0} = 5477\, \mathring{\rm A}$|⁠. It implies a disc size a factor of 1.6 times larger than prediction from the standard disc model with L / L Edd = 0.4. This is consistent with previous studies in which larger than expected disc sizes were measured. [ABSTRACT FROM AUTHOR]

This is a study of spectral and photometric observations of the binary system with an X-ray component V725 Tauri=A0535+262. It consists of a giant star HDE 245770 of spectral class O9.7 and the pulsar A0535+26 with a pulsation period of ~103 s. Active stages of this object, accompanied by "giant" X-ray outbursts, have been observed repeatedly. The last events occurred during 2009-2011. Our studies in 2017-2020 yielded the following data: over the last three years the B and V band brightness of the object has remained at a high level and began to decrease at the end of 2019. Here, beginning in 2016 a gradual increase in the radiative fluxes in the Hβ and Hα emission lines has been observed. At present the equivalent widths of these lines exceed the values recorded during the time of the gigan X-ray outburst of 2011. Previous studies have shown that a similar combination of the characteristics of this object, specifically an increase in emission line fluxes as the brightness decreases. is detected just before the onset of an active stage. [ABSTRACT FROM AUTHOR]

Atmospheric Ar:H2 plasma is an eco-friendly option for the reduction of metal oxides. For better reduction performance and safety concern, the hydrogen gas injected into the reactor should be monitored. A hydrogen flow rate estimation system is presented in this paper by using an artificial neural network (ANN) model fed with features of optical emission spectra of the plasma. ANN models are studied with two different sets of input, i.e. for the first case the inputs to the model are the three features of Hα line such as the peak intensity count, full-width half maximum and area under Hα line, while for the second case, the peak intensity count of a group of emission lines like Hα, Ar I, O I, K I, Na D lines are considered as the inputs. ANN model is developed for estimating four different sets of hydrogen flow rates 5, 8, 10 and 12 litres per minute (lpm) when the argon flow rate is constant at 10 lpm. For both the input features, the model performances are compared, and it is shown that improved estimation accuracy is observed from the second case, i.e. from peak intensity count of a group of emission lines instead of only hydrogen emission line. [ABSTRACT FROM AUTHOR]

The character of the interaction of two gaseous components which are a structural feature of the nucleus of the Seyfert galaxy NGC 1275 is established during the epoch of a minimum in its activity. A bank of emission line profiles (Hβ and O[III] λ5007Å) obtained from observations on the 1.5-m Russian-Turkish telescope (RTT-150) in January 2012 is used. The physical characteristics (Te, ne) of the emission region of the nebular line [OIII] are calculated for this observation epoch and are compared with other published data. The changes in an important spectral characteristic of the emission from the galaxy nucleus (Ewλ, the equivalent with of the Hβ and O[III] λ5007Å lines) are tracked during individual nights and from night-to-night. These studies show that the two "interpenetrating" gaseous components retain a high level of interaction over a long period of time. [ABSTRACT FROM AUTHOR]

We employ optical spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) combined with X-ray and radio data to study the highly-ionized gas (HIG) phase of the feedback in a sample of five local nearby Active Galactic Nuclei (AGN). Thanks to the superb field of view and sensitivity of MUSE, we found that the HIG, traced by the coronal line [Fe vii] λ6089, extends to scales not seen before, from 700 pc in Circinus and up to ∼2 kpc in NGC 5728 and NGC 3393. The gas morphology is complex, following closely the radio jet and the X-ray emission. Emission line ratios suggest gas excitation by shocks produced by the passage of the radio jet. This scenario is further supported by the physical conditions derived for the HIG, stressing the importance of the mechanical feedback in AGN with low-power radio jets. [ABSTRACT FROM AUTHOR]

The symbiotic object EG And consists of a giant star (M4III) and a white dwarf. Numerous studies of this object show that its light curve has two minima. There are different hypotheses regarding the source of the secondary minimum, but the problem has not yet been solved. In this paper we present data from photometric and spectral observations of EG And during 2009-2018: B, V, and R magnitudes in the Johnson system and fluxes in the Hβ and Hα emission lines. An analysis of these data showed that the emission fluxes correlate with the orbital phase. The highest fluxes are observed near the secondary minimum. At the same time, emission fluxes are still observed in the primary minimum but attenuated by roughly a factor of 7-10. This indicates that the size of the ionized zone exceeds that of the giant star. On the whole, the light curve for 2009-2018 is consistent with previous photometric data. Rapid (over a few minutes) fluctuations in the brightness of this object are detected in the V and R bands with amplitudes of ~0m.15 and 0m.35, respectively. [ABSTRACT FROM AUTHOR]

We explore the origin of fast molecular outflows that have been observed in active galactic nuclei (AGNs). Previous numerical studies have shown that it is difficult to create such an outflow by accelerating existing molecular clouds in the host galaxy, as the clouds will be destroyed before they can reach the high velocities that are observed. In this work, we consider an alternative scenario where molecules form in situ within the AGN outflow. We present a series of hydro-chemical simulations of an isotropic AGN wind interacting with a uniform medium. We follow the time-dependent chemistry of 157 species, including 20 molecules, to determine whether molecules can form rapidly enough to produce the observed molecular outflows. We find H2 outflow rates up to 140M☉ yr-1, which is sensitive to density, AGN luminosity, and metallicity.We compute emission and absorption lines of CO, OH, andwarm (a few hundred K) H2 from the simulations in post-processing. The CO-derived outflow rates and OH absorption strengths at solar metallicity agree with observations, although the maximum line-of-sight velocities from the model CO spectra are a factor ≈2 lower than is observed. We derive a CO (1-0) to H2 conversion factor of αCO(1-0) = 0.13M☉ (K km s-1 pc2)-1, 6 times lower than is commonly assumed in observations of such systems. We find strong emission from the mid-infrared lines of H2. The mass of H2 traced by this infrared emission is within a few per cent of the total H2 mass. This H2 emission may be observable by JamesWebbSpaceTelescope. [ABSTRACT FROM AUTHOR]

We present a detailed study of the kinematic, chemical and excitation properties of the giant Ly α emitting nebula and the giant HI absorber associated with the z = 2.92 radio galaxy MRC 0943-242, using spectroscopic observations from Very Large Telescope (VLT)/Multi Unit Spectroscopic Explorer (MUSE), VLT/X-SHOOTER and other instruments. Together, these data provide a wide range of rest-frame wavelength (765-6378 Å at z = 2.92) and 2D spatial information. We find clear evidence for jet gas interactions affecting the kinematic properties of the nebula, with evidence for both outflows and inflows being induced by radiomode feedback. We suggest that the regions of relatively lower ionization level, spatially correlated with the radio hotspots, may be due to localized compression of photoionized gas by the expanding radio source, thereby lowering the ionization parameter, or due to a contribution from shock-heating. We find that photoionization of supersolar metallicity gas (Z/Z☉ = 2.1) by an active galactic nuclei-like continuum (α =-1.0) at a moderate ionization parameter (U = 0.018) gives the best overall fit to the complete X-SHOOTER emission-line spectrum. We identify a strong degeneracy between column density and Doppler parameter such that it is possible to obtain a reasonable fit to the HI absorption feature across the range log N(H I/cm-2 ) = 15.20 and 19.63, with the two best fitting occurring near the extreme ends of this range. The extended HI absorber is blueshifted relative to the emission-line gas, but shows a systematic decrease in blueshift towards larger radii, consistent with a large-scale expanding shell. [ABSTRACT FROM AUTHOR]

UV and optically selected candidates for stellar tidal disruption events (TDEs) often exhibit broad spectral features (He II emission, Hα emission, or absorption lines) on a blackbody-like continuum (104 K ≲ T ≲ 105 K). The lines presumably emit from TDE debris or circumnuclear clouds photoionized by the flare. Line velocities however are much lower than expected from a stellar disruption by supermassive black hole (SMBH), and are somewhat faster than expected for the broad line region (BLR) clouds of a persistently active galactic nucleus (AGN). The distinctive spectral states are not strongly related to observed luminosity and velocity, nor to SMBH mass estimates. We use exhaustive photoionization modelling to map the domain of fluxes and cloud properties that yield (e.g.) an He-overbright state where a large He II(4686 Å)/H α line ratio creates an illusion of helium enrichment. Although observed line ratios occur in a plausible minority of cases, AGN-like illumination cannot reproduce the observed equivalent widths. We therefore propose to explain these properties by a light-echo photoionization model: the initial flash of a hot blackbody (detonation) excites BLR clouds, which are then seen superimposed on continuum from a later, expanded, cooled stage of the luminous source. The implied cloud mass is substellar, which may be inconsistent with a TDE. Given these and other inconsistencies with TDE models (e.g. host-galaxies distribution) we suggest to also consider alternative origins for these nuclear flares, which we briefly discuss (e.g. nuclear supernovae and starved/subluminous AGNs). [ABSTRACT FROM AUTHOR]

Recently, an unknown emission line at E ~3.5 keV from several astrophysical objects has been detected. The line is suggested to be originating from decaying dark matter particles. The results have drawn great attention from the astrophysics and particle physics community. Since the detected line is significantly weak there has also been a long debate over the origin of this mysterious signal. The most accepted scenario is a radiatively decaying sterile neutrino of 7.1 keV in mass producing a monochromatic 3.5 keV line, which is observable in X-ray energy ranges. The problem has not been settled and further observations from more objects are needed to verify the detection in order to constrain the physical properties and the nature of the signal. In this paper, we present the current situation and provide further insights into the subject. [ABSTRACT FROM AUTHOR]

Data from long-term spectral observations of two young planetary nebulae are presented. A significant enhancement of the radiation fluxes in all emission lines and a higher degree of ionization of the gas are detected in the spectrum of M1-46. The opposite effect is observed in the spectrum of M1-65. Over 10 years (2005-2015) the radiative fluxes in the emission lines fell by a factor of 2-3, after which they began to increase. The cause of the observed variability may be a change in the temperature of the central star or a change in the inhomogeneous structure of the nebula through which the ionizing radiation passes. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Physics is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The discovery of exoplanets and the desire to understand their atmospheric chemical composition and habitability provides a new rationale for understanding the radiation from X-rays to radio wavelengths emitted by their host stars. Semiempirical models of stellar atmospheres that include accurate treatment of radiative transfer of all important atoms, ions, and molecules provide the essential basis for understanding a star's emitted radiation that is our main data source for characterizing a star and the radiation environment of its exoplanets. In Solar-type and cooler stars, the ultraviolet and extreme ultraviolet radiation formed in their chromospheres and transition regions drive the photochemistry in exoplanet atmospheres. In this review, I describe and critique the development of semiempirical static and time-dependent models of the chromospheres and transition regions of the Sun and cooler stars as well as the spectroscopic diagnostics upon which these models are based. The related topics of stellar coronae and winds and their theoretical bases are beyond the scope of this review. [ABSTRACT FROM AUTHOR]

The results of spectral and photometric observations of the emission object CH Cyg are presented. The active stage of CH Cyg during 2014-2015 showed up as an increase in the brightnesses to B~7.8 and V~6.8, intensification of the continuum, and increased fluxes in emission lines. A rapid, within days, variability in the emission line profiles was observed. The velocities of individual absorption components were as high as ~3000 km/s. [ABSTRACT FROM AUTHOR]

Based on the gravitational red shift, which is a prediction of Einstein's general relativity theory, of broad optical emission lines in active galactic nuclei (AGNs), a new method is proposed to estimate the virial factors f in measuring black hole masses MRM by the reverberation mapping of AGNs. The factors f can be measured based on two physical quantities, i.e. the gravitational red shifts zg and the full widths at half maxima vFWHM of broad lines. In the past, it has been difficult to determine the factors f for individual AGNs. We apply this new method to several reverberation-mapped type 1 Seyfert galaxies. There is a correlation between f and the radius of the broad-line region (BLR) rBLR, f = 5.4r0.3BLR, for the gravitationally red-shifted broad lines He II, HeI, Hβ and Hα in the narrow-line type 1 Seyfert galaxy (NLS1) Mrk 110. This correlation results from the influence of the radiation pressure of the accretion disc on the BLR clouds. This influence seems to be more important than usually thought so in AGNs. Mrk 110 has f ≈ 8-16, distinctly larger than the mean f ≈1 usually used to estimate MRM for vFWHM. NGC 4593 and NLS1 Mrk 486 have f ≈3 and f ≈9, respectively. Higher f values of several tens are derived for three other NLS1s. There is a correlation between f and accretion rate Mf=1, f = 6.8M0.4 f=1 for five objects, where Mf=1 = M•/LEddc -2 as f = 1 is assumed when estimating MRM used in the Eddington luminosity LEdd, M• is the mass accretion rate, and c is the speed of light. These larger f values will produce higher MRM values and lower Eddington ratios. [ABSTRACT FROM AUTHOR]

Based on the gravitational red shift, which is a prediction of Einstein's general relativity theory, of broad optical emission lines in active galactic nuclei (AGNs), a new method is proposed to estimate the virial factors f in measuring black hole masses MRM by the reverberation mapping of AGNs. The factors f can be measured based on two physical quantities, i.e. the gravitational red shifts zg and the full widths at half maxima vFWHM of broad lines. In the past, it has been difficult to determine the factors f for individual AGNs. We apply this new method to several reverberation-mapped type 1 Seyfert galaxies. There is a correlation between f and the radius of the broad-line region (BLR) rBLR, f = 5.4r0.3 BLR, for the gravitationally red-shifted broad lines He II, HeI, Hβ and Hα in the narrow-line type 1 Seyfert galaxy (NLS1) Mrk 110. This correlation results from the influence of the radiation pressure of the accretion disc on the BLR clouds. This influence seems to be more important than usually thought so in AGNs. Mrk 110 has f ≈ 8-16, distinctly larger than the mean {f} ≈ 1 usually used to estimate MRM for vFWHM. NGC 4593 and NLS1 Mrk 486 have f ≈ 3 and f ≈ 9, respectively. Higher f values of several tens are derived for three other NLS1s. There is a correlation between f and accretion rate Mf=1, f = 6.8M0.4 f=1 for five objects, where Mf=1 = M•/LEddc -2 as f = 1 is assumed when estimating MRM used in the Eddington luminosity LEdd, M• is the mass accretion rate, and c is the speed of light. These larger f values will produce higher MRM values and lower Eddington ratios. [ABSTRACT FROM AUTHOR]

We present a spectral variability study of a sample of about 25 bright blazars, based on optical spectroscopy. Observations cover the period from the end of 2008 to mid 2015, with an approximately monthly cadence. Emission lines have been identified and measured in the spectra, which permits us to classify the sources into BL Lac-type or FSRQs, according to the commonly used EW limit. We have obtained synthetic photometry and produced colour-magnitude diagrams which show different trends associated with the object classes: generally, BL Lacs tend to become bluer when brighter and FSRQs become redder when brighter, although several objects exhibit both trends, depending on brightness. We have also applied a pattern recognition algorithm to obtain the minimum number of physical components which can explain the variability of the optical spectrum. We have used NMF (Non-Negative Matrix Factorization) instead of PCA (Principal Component Analysis) to avoid un-realistic negative components. For most targets we found that 2 or 3 meta-components are enough to explain the observed spectral variability. [ABSTRACT FROM AUTHOR]

We present a preliminary analysis of X-ray data of quasars in the context of the 4D eigenvector 1 parameter space (Sulentic et al. 2000a, b). 4DE1 serves as a surrogate H-R diagram for representing empirical diversity among quasars and identifying the physical drivers of the diversity. The soft X-ray spectral index (гsoft) was adopted as one of the key 4DE1 that correlates contrasting extremes in Type 1 properties. 4DE1 motivated the hypothesis of two quasar populations (A and B) divided by L/LEDD ≈ 0.2. Pop. A is a largely radio-quiet population with FWHM Hβ < 4000 km/s and often showing a soft X-ray excess. Pop. B is a mix of radio-quiet and a majority of RL quasars shows only a hard X-ray power-law SED. The X-ray separation was based upon earlier ROSAT and ASCA data but we now confirm this dichotomy with large samples of X-ray spectra obtained with XMM-Newton and SWIFT. One popular idea connects the soft excess in Pop. A quasars as a signature of thermal emission from a hot accretion disk in sources radiating close to the Eddington limit. [ABSTRACT FROM AUTHOR]

We present the results of our spectroscopic studies of the nebula NGC 6857 located in a region of current star formation. Data on the surface brightness distribution in the central region of the nebula (∼60″ × 60″) in the H α, H β, [OIII], 5007 Å, [N II], 6548, 6583 Å, [S II], 6717, 6731 Å, and He I, 6678 Å lines have been obtained with an angular resolution of ∼4.″5 × 4.″5. The zones of maximum surface brightness and the region of maximum gas ionization ratio are located 12″ south of the central star, which may suggest the existence of a second gas ionization source. [ABSTRACT FROM AUTHOR]

The broad-line region (BLR) of flat-spectrum radio quasars (FSRQs) could have a "flat" geometrical structure to allow GeV gamma-ray photons to escape, to produce the observed gamma-ray flares with short timescales. In this paper, we collect the quasisimultaneous spectral energy distributions (SEDs) of the FSRQ 3C 454.3 obtained by the multi-wavelength campaigns spanning from 2007 July to 2011 January, and use a model with a "flat" structure BLR, an accretion disc and a dust torus to explain the SEDs of gamma-ray outbursts. We obtain the following results: (i) the jet is almost in equipartition between magnetic and particle energy densities during the outbursts; (ii) when the emitting region is located inside the cavity of the BLR, the covering factor fBLR of the BLR is very small-as the emitting region goes into the BLR structure, fBLR increases; (iii) the aperture angle α describing the BLR structure is about 45°; (iv) the central black hole mass is about 5×108 M⊙ rather than 4.4×109 M⊙. [ABSTRACT FROM AUTHOR]

A solar coronagraph above the Earth's atmosphere provides ideal conditions to study various properties of coronal plasma such as pressure, density, and temperature perturbation leading to the existence of waves, the topology of magnetic fields, dynamical nature of coronal loops & CME's and space weather predictions. Keeping in view of these scientific objectives of coronal dynamics, a 20 cm coronagraph is being planned to be launched in space by ISRO. The solar corona will be imaged in two bright coronal emission lines (viz., the green and the red-lines at 530.3 nm and 637.4 nm respectively). The field-of-view (FOV) of interest in the solar corona is from 1.05 to 3.0 solar radii in order to maximize the science outcome of coronal dynamics and also to provide complementary data to the other existing/planned space missions. The optical design of the coronagraph has a 20-cm diameter off-axis parabolic mirror as its main optical imager. The mirror has a stringent requirement of 0.1-0.15 nm micro-roughness in order to provide a scatter light of less than 5-ppm. This mirror and other reflecting optics required for the coronagraph are being fabricated at LEOS, ISAC. The full optical design is optimized for the diffraction-limited imaging capabilities and is discussed in this paper along with the scientific objectives of the payload. [ABSTRACT FROM AUTHOR]

Context. Supermassive black holes in the centers of active galactic nuclei (AGN) are surrounded by broad-line regions (BLRs). The broad emission lines seen in the AGN spectra are emitted in this spatially unresolved region. Aims. We intend to obtain information on the structure and geometry of this BLR based on observed line profiles. Methods. We modeled the rotational and turbulent velocities in the line-emitting region on the basis of the line-width FWHM and line dispersion σline of the variable broad emission lines in NGC5548. Based on these velocities we estimated the height of the lineemitting regions above the midplane in the context of their distances from the center. Results. The broad emission lines originate at distances of 2 to 27 light days from the center. Higher ionized lines originate in the inner region (⩽13 light days) in specific filamentary structures 1 to 14 light days above the midplane. In contrast, the Hβ line is emitted in an outer (6-26 light days), more flattened configuration at heights of 0.7 to 4 light days only above the midplane. Conclusions. The derived geometry of the line-emitting region in NGC5548 is consistent with an outflowing wind launched from an accretion disk. [ABSTRACT FROM AUTHOR]

The rare-earth ions cerium ii, lanthanum ii, dysprosium ii, and additionally zirconium ii and iron ii, are seen as weak emission features in the wings of the solar Ca ii H and K lines. The strength of these emission lines increases on the disk toward the limb. We provide recent high-resolution observations at disk center and at the limb. The identity of the weak lines is re-worked. We point out the unique role of eclipse spectra in distinguishing between the photospheric and chromospheric origins of emission lines. It is then demonstrated from our full disk (Sun-as-a-Star) and center disk archives, 1974 - 2010, that no activity cycle related signal is evident (save for the H and K lines themselves). [ABSTRACT FROM AUTHOR]

We performed high resolution spectroscopy of the solar corona during the total solar eclipse of 22 July 2009 in two emission lines: the green line at 5303 Å due to Fe xiv and the red line at 6374 Å due to Fe x, simultaneously from Anji (latitude 30°28.1′ N; longitude 119°35.4′ E; elevation 890 m), China. A two-mirror coelostat with 100 cm focal length lens produced a 9.2 mm image of the Sun. The spectrograph using 140 cm focal length lens in Littrow mode and a grating with 600 lines per millimeter blazed at 2 μm provided a dispersion of 30 mÅ and 43 mÅ per pixel in the fourth order around the green line and third order around the red line, respectively. Two Peltier cooled 1k × 1k CCD cameras, with a pixel size of 13 μm square and 14-bit readout at 10 MHz operated in frame transfer mode, were used to obtain the time sequence spectra in two emission lines simultaneously. The duration of totality was 341 s, but we could get spectra for 270 s after a trial exposure at an interval of 5 s. We report here on the detection of intensity, velocity, and line width oscillations with periodicity in the range of 25 - 50 s. These oscillations can be interpreted in terms of the presence of fast magnetoacoustic waves or torsional Alfvén waves. The intensity ratios of green to red emission lines indicate the temperature of the corona to be 1.65 MK in the equatorial region and 1.40 MK in the polar region, relatively higher than the expected temperature during the low activity period. The width variation of the emission lines in different coronal structures suggests different physical conditions in different structures. [ABSTRACT FROM AUTHOR]

We analyze the spectral variability for two narrow line Seyfert 1 galaxies, PG 1700+518 and NGC 4051 using the spectral decomposition method. We focus on their optical Fe ii variability to investigate the origin of Fe ii in AGNs. For PG 1700+518, we find that the Fe ii size is about 200 light-days, which is consistent with the H β size derived from the empirical R-L relation. For NGC 4051, the [O iii] 5007 Å flux is strongly correlated with continuum flux, suggesting that we should recalibrate the spectral flux on a scale defined by [O iii] flux. The corrected light curves of Fe ii, H β, He ii, f(5100 Å) are given here. A detailed analysis will be given in the near future. [ABSTRACT FROM AUTHOR]

We analyze the optical spectra of Fairall 9, a luminous Seyfert 1 galaxy. They are obtained from the AGN Watch program that has monitored this object for 9 months. The flux and variation of the optical FeII complex is measured using multi-component profile modeling with FeII templates. A convincing intrinsic Baldwin Effect (BEff) of optical FeII emission blends in Fairall 9 is discovered for the first time. The variation of FeII/Hβ ( R) in Fairall 9 is obtained. We also detect a marginal anti-correlation between R and the continuum flux in its spectra. This anti-correlation and the relatively broad profile of Hβ in this galaxy support the dichotomy reported by Wang et al. (2005). [ABSTRACT FROM AUTHOR]

In this work, we revisited the relationship between the subclasses of blazars (X–ray selected BL Lacertae objects (XBLs), radio selected BL Lacertae objects (RBLs), and flat spectrum radio quasars (FSRQs)) based on a sample of blazars. We found that the FSRQs–RBLs–XBLs relationship is clear in their bolometric luminosity, emission line luminosity and the accretion ratio with VFSRQs > VRBLs > VXBLs, where V stands for the three parameters. However, there is no clear difference amongst their central black hole masses. The bolometric luminosity is closely correlated with the emission line luminosity and the accretion ratio. [ABSTRACT FROM AUTHOR]

We obtained the images of the eastern part of the solar corona in the Fe xiv 530.3 nm (green) and Fe x 637.4 nm (red) coronal emission lines during the total solar eclipse of 29 March 2006 at Manavgat, Antalya, Turkey. The images were obtained using a 35 cm Meade telescope equipped with a Peltier-cooled 2k × 2k CCD and 0.3 nm pass-band interference filters at the rates of 2.95 s (exposure times of 100 ms) and 2.0 s (exposure times of 300 ms) in the Fe xiv and Fe x emission lines, respectively. The analysis of the data indicates intensity variations at some locations with period of strongest power around 27 s for the green line and 20 s for the red line. These results confirm earlier findings of variations in the continuum intensity with periods in the range of 5 to 56 s by Singh et al. ( Solar Phys. 170, 235, ). The wavelet analysis has been used to identify significant intensity oscillations at all pixels within our field of view. Significant oscillations with high probability estimates were detected for some locations only. These locations seem to follow the boundary of an active region and in the neighborhood, rather than within the loops themselves. These intensity oscillations may be caused by fast magneto-sonic waves in the solar corona and partly account for heating of the plasma in the corona. [ABSTRACT FROM AUTHOR]

The masses of the central supermassive black holes (BHs) and the Eddington ratios for a sample of 65 young radio galaxies [27 gigahertz-peaked spectrum (GPS) and 38 compact steep-spectrum (CSS) sources] are estimated by various methods. We find that the average BH mass of these young radio galaxies is , which is less than that of radio loud quasi-stellar objects (QSOs) and low-redshift radio galaxies . The CSS/GPS sources have relatively high Eddington ratios with average ratio , which are similar to those of narrow-line Seyfert 1 galaxies (NLS1s). It suggests that the CSS/GPS sources may not only be in the early stage of radio activities, but also in the early stage of their accretion activities. We find that the young radio galaxies as a class deviate systematically from the relation defined by nearby inactive galaxies, when using as a surrogate for the stellar velocity dispersion . There is no significant correlation between the deviation of the [O iii] emission line width, and the jet/accretion power, where are calculated from the Tremaine et al. relation using the estimated BH masses. However, we find that the deviation in young radio galaxies is well correlated with the Eddington ratio, and this correlation is found to be similar to that of radio quiet active galactic nuclei (AGN) (QSOs/NLS1s) where the radio jet is absent or weak. We suggest that the accretion activities may still play an important role in shaping the kinematics of [O iii] narrow line in these young radio galaxies. [ABSTRACT FROM AUTHOR]

1009-0252 is a Quasi Stellar Object (QSO) with three components A, B, C. A, B are thought to be the result of gravitational lensing of one object, and A, C constitute a close pair with redshifts 2.74 and 1.62 respectively. Close separation pairs of QSOs with discordant redshifts have received special attention in recent years, probably because of the possibility that they may be physically associated, implying non-cosmological redshifts. Attempts have been made to explain their occurrences due to the effect of gravitational lensing. However, gravitational lensing has not offered a completely satisfactory explanation for this triplet. Furthermore, examination revealed some inadequacies and inconsistencies in the redshift identification of the observed lines in the component A. Observational results of 1009-0252 therefore remain puzzling. We propose an alternative explanation by suggesting that A, B actually constitute a close pair and C is an unrelated object in the field. We show that the observed spectrum of A can be interpreted as blueshifted. This implies that A, B are two separate objects, one (A) approaching us and the other (B) receding from us, and are not the result of gravitational lensing of a single object. The oppositely directed pair A, B may have been ejected due to the merger of two galaxies. [ABSTRACT FROM AUTHOR]

Spectroscopic mapping of planetary nebulae (PNe) is particularly useful to capture the richness in terms of physical and chemical properties that exist in these objects. The advent of the multi-unit spectroscopic explorer (MUSE), a large integral field unit mounted on the ESO Very Large Telescope, allow us to obtain this information over the whole face of galactic PNe in a reasonable amount of time. This in turn reveals a wealth of information that can bring insight into this structural complexity. Here we discuss new results from commissioning data for the physical properties of IC 418 and succinctly review recently published results on two additional targets (NGC 3132 and NGC 7009). For the newly-analysed PN, electron densities are high with n e ([S ii]) displaying a completely different structure than n e ([Cl iii]). The electron temperature was relatively uniform, but somewhat higher at the rim as measured by two of the three used diagnostics ([S iii] 6312/9069, and [Ar iii] 5192/7136). The joint results for the three PNe amply illustrate the potential of MUSE for the study of galactic PNe. [ABSTRACT FROM AUTHOR]

The frontier for ultraviolet studies of active galactic nuclei is the time domain: in particular, reverberation mapping of the broad emission-line region can lead to determination of the geometry and kinematics of accretion flows and winds as well as accurate measurement of the masses of the central black holes. Here we review progress to date and describe how additional advances can be made with an ultraviolet telescope of modest aperture. [ABSTRACT FROM AUTHOR]

I briefly review in this paper the main observational properties of relativistically broadened X-ray spectral lines in Galactic Black Holes and Active Galactic Nuclei, and the (scanty) estimates of their frequency in the corresponding parent populations. The available measurements allow us to derive some constraints on the black hole spin and mass, and on the accretion disk geometry and illumination. [ABSTRACT FROM AUTHOR]

Using spectral technique, analyses of some astrophysical data from the EUVE satellite in the Extreme Ultraviolet region on accretion disk of some cataclysmic variable were carried out. A number of strong emission lines in 14 CVs were discovered. Most CVs follow a similar trend in the number of ionized elements present in their spectrum while some have very few or no ionized elements in their spectrum. The AM Herculis star, which has the weakest magnetic field of all seven magnetic CVs studied, contain no ionized elements in its EUVE spectroscopy. However, for the rest of the CVs, there is sufficient evidence to conclude that the accretion disks of CVs are highly ionized. This implies also that the accretion disks of other astrophysical objects could be equally highly ionized. This result is in agreement with the suggestion that the most promising candidate for providing the angular momentum transport mechanism during the outburst is magneto hydrodynamics turbulence. [ABSTRACT FROM AUTHOR]